Tag Archives: earthquake prediction

Earthquake Lights & Rifts

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Mysterious Earthquake Lights Linked To Rifts

Saturday, January 4, 2014

Rare earthquake lights are more likely to occur on or near rift environments, where subvertical faults allow stress-induced electrical currents to flow rapidly to the surface, according to a new study published in the Jan./Feb. issue of Seismological Research Letters.

An earthquake light is an unusual luminous aerial phenomenon that reportedly appears in the sky at or near areas of tectonic stress, seismic activity, or volcanic eruptions. Once commonly challenged, it was not until photographs were taken during the Matsushiro earthquake swarm in Nagano, Japan (which occurred from 1965 through 1967) that the seismology community acknowledged their occurrence.

From the early days of seismology, the luminous phenomena associated with some earthquakes have intrigued scholars. Earthquake lights (EQL) appear before or during earthquakes, but rarely after.

Earthquake lights from Tagish Lake, Yukon-Alaska border region, around the 1st of July, probably 1972 or 1973 (exact date unknown). Estimated size: 1m diameter. Closest orbs slowly drifted up the mountain to join the more distant ones.

Credit: Photo credit: Jim Conacher, used with permission

EQL take a variety of forms, including spheres of light floating through the air. Seconds before the 2009 L’Aquila, Italy earthquake struck, pedestrians saw 10-centimeter high flames of light flickering above the stone-paved Francesco Crispi Avenue in the town’s historical city center. On Nov. 12, 1988, a bright purple-pink globe of light moved through the sky along the St. Lawrence River near the city of Quebec, 11 days before a powerful quake. And in 1906, about 100 km northwest of San Francisco, a couple saw streams of light running along the ground two nights preceding that region’s great earthquake.

Continental rift environments now appear to be the common factor associated with EQL. In a detailed study of 65 documented EQL cases since 1600 A.D., 85 percent appeared spatially on or near rifts, and 97 percent appeared adjacent to subvertical faults (a rift, a graben, strike-slip or transform fault). Intraplate faults are associated with just 5 percent of Earth’s seismic activity, but 97 percent of documented cases of earthquake lights.

“The numbers are striking and unexpected,” said Robert Thériault, a geologist with the Ministère des Ressources Naturelles of Québec, who, along with colleagues, culled centuries of literature references, limiting the cases in this study to 65 of the best-documented events in the Americas and Europe.

“We don’t know quite yet why more earthquake light events are related to rift environments than other types of faults,” said Thériault, “but unlike other faults that may dip at a 30-35 degree angle, such as in subduction zones, subvertical faults characterize the rift environments in these cases.”

Two of the 65 EQL events are associated with subduction zones, but Thériault suggests there may be an unknown subvertical fault present. “We may not know the fault distribution beneath the ground,” said Thériault. “We have some idea of surface structures, but sedimentary layers or water may obscure the underlying fault structure.”

While the 65 earthquakes ranged in magnitude, from M 3.6 to 9.2, 80 percent were greater than M 5.0. The EQL varied in shape and extent, though most commonly appeared as globular luminous masses, either stationary or moving, as atmospheric illuminations or as flame-like luminosities issuing from the ground.

Timing and distance to the epicenter vary widely. Most EQL are seen before and/or during an earthquake, but rarely after, suggesting to the authors that the processes responsible for EQL formation are related to a rapid build-up of stress prior to fault rupture and rapid local stress changes during the propagation of the seismic waves. Stress-activated mobile electronic charge carriers, termed positive holes, flow swiftly along stress gradients. Upon reaching the surface, they ionize air molecules and generate the observed luminosities.

Eyewitness reports and security cameras captured a large number of light flashes during the 2007 Pisco, Peru M 8.0 earthquake. Together with seismic records obtained on a local university campus, the automatic security camera records allow for an exact timing and location of light flashes that illuminated a large portion of the night sky. The light flashes identified as EQL coincided with the passage of the seismic waves.

Thériault likes the account of a local L’Aquila resident, who, after seeing flashes of light from inside his home two hours before the main shock, rushed his family outside to safety.

“It’s one of the very few documented accounts of someone acting on the presence of earthquake lights,” said Thériault. “Earthquake lights as a pre-earthquake phenomenon, in combination with other types of parameters that vary prior to seismic activity, may one day help forecast the approach of a major quake,” said Thériault.

from:    http://beforeitsnews.com/earthquakes/2014/01/mysterious-earthquake-lights-linked-to-rifts-2483590.html

The L’Aquila Earthquake Trial Results

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The Verdict of the l’Aquila Earthquake Trial Sends the Wrong Message

Rubble from a collapse house covered a car after the 2009 l’Aquila earthquake in Italy. Image: Alessandro Giangiulio / Flickr.

By this time, many of you have seen the verdict for the people on trial over the 2009 l’Aquila earthquake. Judge Marco Billi sentenced the seven scientists, engineers and officials to 6 years in prison – 2 years more than the prosecution suggested – over the manslaughter charges stemming from the earthquake that killed over 300 people. The trial has been a flashpoint for geoscientists as many have seen it as a trial over the idea that geologists should be able to “predict” earthquakes. This is somewhat misleading as the prosecution was actually claiming the seven on trial were accused of “having carried out a superficial analysis of seismic risk and of having provided false reassurances to the public.” This doesn’t mean they got a “prediction” wrong, but rather that they didn’t fully understand the risk for l’Aquila, thus put people’s lives in danger. However, this whole trial, in its misguided attempt to find someone to blame for a blameless geologic event, sends the wrong message about how to deal with hazard assessment and mitigation.

 

Now, I’m not going to rehash the whole trial – you can see some excellent summaries in Nature News and The New York Times. However, let’s get this straight. Say what you will about whether the seven adequately did their job in mitigating against the disaster, but convicting them of manslaughter? That is what makes this case so egregious. If you look up a definition of manslaughter (and it varies from country to country), this likely falls under the criminally negligent variety, where “a defendant intentionally puts himself in a position where he will be unaware of facts which would render him liable.” This suggests that the seven on trial caused the 308 deaths from the l’Aquila earthquake by ignoring the facts presented. People who survived the earthquake and the prosecution claim that the scientists should have known a large earthquake was coming because there had been many small earthquakes that preceded it (so-called “foreshocks“, which have not been proven to be predictive of a larger earthquake). However, the scientists and officials instead said that the earthquakes were releasing energy on local faults, reducing the threat of an earthquake. Chris Rowan does a great job explaining why both of these positions are wrong. It all boils down to the idea of what could actually be deduced from the facts in hand. Should government officials and scientists have proclaimed that an earthquake would occur in days when no data existed that confirmed this? (And no, saying that the earthquake did occur is not evidence – that is hindsight.)

So, we’re back in the same quandry we often find ourselves when it comes to geologic hazard mitigation – prediction versus probability. Indeed, the city of l’Aquila does lie in a region of high seismic hazard for Italy. This was not a fact that was hidden from the public by government officials – in fact, most people who live in Italy should know that earthquakes are not uncommon across the country. However, even with swarms of small earthquakes, there is no way that any seismologist could say that yes, a large earthquake will happen within a week*. That is the realm of prediction. Alternatively, they should not rule out the possibility that a large earthquake could occur in a region of high seismic hazard. So, the answer is, yes, at some point, a large earthquake will occur here. It isn’t satisfying, but it is what the data will bear. However, that isn’t what people want to hear. They want to know “should I leave my house tomorrow? Tuesday?” Without such an imposed deadline, many times the perceived threat just fades into the background of everyday life, like car accidents or fires.

Why did this trial occur if the science really says there wasn’t anything that could be done? I think it is clearly so that people can have someone to blame. The 7 on trial did say something that can be perceived as reassuring mere days before the tragedy, so clearly, they are the reason those 308 people died. Have a big, flashy show trial and charge them with something frightful. Now, that’ll get people’s attention and solve this problem … forever! Of course it won’t – in fact, it might make proper hazard assessment and discussion even more difficult in Italy because people will be afraid that if they get it wrong, they too will go to prison. It might lead to more “false positives” that erode the public’s confidence in the ability to judge the hazard risk in areas around the country. You’ve create a situation where hazard geoscientists are caught between a literal rock and a hard place – don’t emphasize enough and something happens, you go to prison; overemphasize and cause panic, you lose the public’s trust. I hope this doesn’t lead to a culture of “geologic malpractice”, where any discussion of hazards and mitigation are scrutinized after the fact so that lawyers can go after whomever they want to place the blame. Even more startling, there are threats that the Italian government will cut the positions of many scientists in the INGV who are monitoring active volcanoes and other hazards, leaving the country even more vulnerable. It is a perfect recipe for an epic tragedy to occur.

If you do live in a region of high geologic hazard, then you should be prepared for such eventualities, and if you can’t make the preparations, then you should be making sure your government does. By that I mean infrastructure improvements, emergency planning and response, evacuation plans – all the things that you, personally, can’t tackle. You can prepare your home and family as much as you can, but there has to be buy-in across all levels. However, when it comes down to it, a lot of the responsibility falls on the public to be better educated about the hazards they face. Some of that needs to come from the officials and scientists in charge – better outreach, clearer statements, more research – but some of this needs to come from the grassroots where children learn science and hazards. I do know one thing: Witch hunts to find someone to blame for a tragedy have never brought anyone back.

* It is sad that this case also involves the charlatans who claim to be able to “predict” earthquakes. If Giampaolo Giuliani hadn’t bandied about his unsubstantiated claims about radon being used to predict the earthquake – which caused undue panic and uncertainty that the government tried to quell – would these seven be potentially headed to jail?

from:   http://www.wired.com/wiredscience/2012/10/the-verdict-of-the-laquila-earthquake-trial-sends-the-wrong-message/#more-134908